The northern lobe of the White River Ash (WRAn) is part of a bilobate distribution of tephras that originated from the Wrangell Volcanic Field near the border of Alaska, USA, and Yukon, Canada. It is distributed across northeastern Alaska and the northwestern portion of the Yukon. The timing of this eruption has seen little critical analysis relative to the younger and more extensive eastern lobe eruption of the White River Ash. We compiled 38 radiocarbon (14C) dates from above and below the WRAn, and employed several statistical approaches to identify and eliminate or down-weight outliers, combine dates, and different Bayesian models, to provide a revised age estimate for the timing of the WRAn tephra deposition. Our results indicate that the most accurate modeled age estimate for the northern lobe of the White River Ash deposition is between 1689 and 1560 cal BP, with a mean and median of 1625 and 1623 cal BP, respectively. This age range is 90 to 200 years younger than previous age estimates.

As part of the ongoing effort to improve the Northern Hemisphere radiocarbon (14C) calibration curve, this study investigates the period of 856 BC to 626 BC (2805–2575 yr BP) with a total of 403 single-year 14C measurements. In this age range, IntCal13 was constructed largely from German and Irish oak as well as Californian bristlecone pine 14C dates, with most samples measured with a 10-yr resolution. The new data presented here is the first atmospheric 14C single-year record of the older end of the Hallstatt plateau based on an absolutely dated tree-ring chronology. The data helped reveal a major solar proton event (SPE) which caused a spike in the production rate of cosmogenic radionuclides around 2610/2609 BP. This production event is thought to have reached a magnitude similar to the 774/775 AD production event but has remained undetected due to averaging effects in the decadal calibration data. The record leading up to the 2610/2609 BP event reveals a 11-yr solar cycle with varying cyclicity. Features of the new data and the benefits of higher resolution calibration are discussed.

This work shows the results of optically stimulated luminescence (OSL) and radiocarbon (14C) dating applied to mortars of historical structures in northern Italy. All the results are compared with archaeological evidence and thermoluminescence (TL) dating of bricks. The main issue for OSL mortar dating is that the quartz grains contained in the mortar may be only partially bleached, leading to an overestimation of the sample age. In order to identify the best protocol to apply, both multi-grain (MG) and single grain (SG) methods were used. The minimum age model (MAM) statistical approach was applied to refine their accuracy. However, the identification of the bleached grains is not always successful, indicating that further investigations are needed to develop suitable dating protocol. For the 14C technique, a crucial aspect is the selection of anthropogenic calcite. In this work the mortars were treated using a Cryosonic method to select anthropogenic calcite from raw material, and the obtained powder was sieved to select the finer fraction. Unfortunately, only in two cases an acceptable amount of sample could be obtained. All the fractions were dated via accelerator mass spectrometry (AMS), and the results compared with independently obtained dates. The results show that the execution of the dating analysis requires previous characterizations to assess the nature of the mortar components and avoid unusable fractions.

Differential sources of sedimentary organic compounds in a volcanic region were revealed by determining radiocarbon content (Δ14C) of organic compounds in surface sediments from Lake Kawaguchi, at the northern foot of Mount Fuji, central Japan. The Δ14C values of C16 fatty acid (−124‰) and chlorophyll a (Chl a) (−133‰) were similar to the Δ14C of dissolved inorganic carbon (DIC) in surface water (−117‰), suggesting that a significant portion of these compounds originated from modern primary producers with a reservoir age of ~1000 years. On the other hand, a large offset between the Δ14C values of Chl a (−133‰) and those of 132, 173-cyclopheophorbide-a-enol (−169‰) and pheophytin a (−179‰) suggested contributions from older pigments. In addition, the Δ14C of long-chain (C24, C26, and C28) fatty acids (−183 to −75‰) showed a large offset from that of a plant leaf remain (0‰) within sediments, demonstrating that the long-chain fatty acids were affected by substantial contributions from pre-aged terrestrial materials. Overall, the sedimentary organic compounds gave 14C ages older than the plant leaf fragment within sediments; however, the similarity between Δ14C of the C16 fatty acid and DIC implies potential for applying compound-specific radiocarbon analysis as a dating tool in volcanic lake environments.

More than 70 logboats are known in Lithuania and about half of them date before 1800 cal AD. This paper reviews these more ancient logboats, which were discovered in the beds of former or still existing lakes and rivers and present new radiocarbon (14C) dates and wood taxa identifications. Special attention is paid to the logboat found at Šventoji 58, which is at present the oldest 14C-dated (2895–2640 cal BC) logboat found East of the Baltic Sea. Most logboats from the pre-1800s period were 14C dated to medieval and early modern periods and they were made out of pine and oak wood. From a very scarce dataset available it seems that oak wood was introduced into logboat building by Neolithic people, who also brought new technologies in stone tool production. We also noted that 14C dating does not confirm the logboat typology suggested in earlier studies.

Recent archaeological excavations on Rakahanga Atoll, Northern Cook Islands, produced one of the earliest examples of dog (Canis familiaris) remains found on East Polynesian atolls. Direct dating of these and other Pacific Island fauna by AMS is complicated by a number of factors. (1) The animals’ diets may consist of marine and terrestrial protein. (2) Marine 14C is itself a mix of carbon pools with localized offsets that vary over time and space. (3) The region is potentially impacted by inter-hemispheric mixing of atmospheric 14C. Stable isotope analysis of gelatin extracted from dog teeth was used to estimate marine/terrestrial dietary components and paired terrestrial and marine samples were used to constrain local atmospheric and marine carbon offsets. The dates were modeled as a phase in a Bayesian chronological framework using mixed calibration curves. The resulting models confirm the presence of dogs on Rakahanga shortly after the initial colonization of the region and suggest that dogs were among the species that accompanied voyagers as they discovered and settled new islands. These methods can be applied to accurately date any marine-influenced terrestrial vertebrate remains in Remote Oceania.

The 14C/12C ratio of living organisms is largely determined by the 14C/12C ratio of consumed diet as well as by the atmospheric 14C concentration together with the body’s metabolic processes. The measured 14C content of living matter compared to the atmospheric radiocarbon level can provide invaluable information about developmental processes. Our aim was to determine the 14C content of ten different tissues of the human eye using the 14C bomb-pulse dating signature. The 14C content of the atmosphere, so called 14C “bomb-pulse” has labeled humanity offering an opportunity to determine these special formation, turnover and substitution courses in biology. The results allowed us to construct a 14C map of the bomb-peak labeled human eye. According to the anatomical location of the tissues, an unexpected picture emerged as in moving from the outer parts towards the inner parts of the eye, the 14C content of each tissue decreased. The data presented here are compatible with the view that the oldest parts of the eye are the sclera, the limbus and the cornea, in this order, and moving further inside, the youngest tissue of the eye is the retina.

In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization.

Direct dates of pottery obtained from food crusts or other organic residues on the vessel surfaces can be affected by a reservoir effect and/or an old wood effect and therefore be unreliable. Hence, there is a need for alternative ways to directly date pottery. Moss is used as temper by several cultural groups of the late 6th to early 4th millennium cal BC in northwestern Europe. After the pottery is fired, charred moss remains are often preserved in the clay, so that relatively short-lived plant material with a direct chronological link to the pottery and human occupation is available for radiocarbon (14C) dating. In this study, charred moss temper is extracted for accelerator mass spectrometry (AMS) 14C dating from pottery of the Swifterbant Culture and Spiere group in the Scheldt river valley (Belgium). The moss dates are then compared to reference dates of organic macro-remains from the same sites and food crust dates with or without a reservoir effect of the same pottery. Eleven out of 13 moss dates are in line with the expected pottery age. The paired dates of moss temper and food crusts from the same potsherds confirm a freshwater reservoir effect (FRE) for the latter. We conclude that moss temper has great potential as a sample material for direct pottery dating. However, more research on the extraction and pretreatment of moss temper as well as on the reliability of moss dates is necessary in the future.

Laser ablation (LA) accelerator mass spectrometry (AMS) is a novel method for rapid online radiocarbon (14C) analysis of carbonates. The quasi-continuous 14C profiles obtained with this technique demand a customized data evaluation protocol to relate the acquired 14C data to the analyzed sample. We take into account the mixing effects due to the minimal counting (integration) time of the AMS, the finite width of the laser beam and the gas washout of the ablation volume. Thereby we mathematically describe our LA setup with a system function that acts on the produced CO/CO2 (COX) from the sample resulting in a mixing of the 14C profiles obtained by AMS analysis. Furthermore, we analyze the long-term target memory effect in the gas ion source and establish a routine for correction. The correction routine is tested with a stalagmite comprising a growth stop that is analyzed at different scanning velocities indicating that only the slow scanning velocity can provide the necessary resolution to determine the width of the growth stop of 365 μm.

Stone and earthen architecture is nearly ubiquitous in the archaeological record of Pacific islands. The construction of this architecture is tied to a range of socio-political processes, and the temporal patterning of these features is useful for understanding the rate at which populations grew, innovation occurred, and social inequality emerged. Unfortunately, this temporal patterning is poorly understood for many areas of the region, including the Sāmoan archipelago. Here, we describe a project directed toward establishing a robust chronology for the construction of these earthen and stone terraces and linear mounds on Ta‘ū Island. Using recent methodological improvements, we highlight the tempo at which different architectural types were constructed on the island and the implications for understanding demographic expansion and changing land tenure practices in the last 1500 years. This research suggests the construction of architecture was largely confined to the 2nd millennium AD with a small number of terraces plausibly built in the 1st millennium AD. This temporal patterning suggests that a reconfiguration of settlement patterns occurred within West Polynesia as people there moved into other regions of Oceania.

After the last damaging earthquake in 2012, an anti-seismic reinforcement project of the cathedral of Modena was designed giving us the opportunity to investigate and date the building materials. Radiocarbon (14C), optically stimulated luminescence (OSL), and thermoluminescence (TL) dating techniques were performed on the vaults with the aim to (1) clarify the construction timing, (2) define the history of the restorations, and (3) explore the possible correlation of the main restoration works to the earthquake chronology deduced from the historic catalog. Preliminary results show that medieval older bricks were reused for most of the original construction. Only lime and non-gypsum mortar was used for the original construction in the 15th century and for later repair of damage caused by earthquakes in the 16th and 17th centuries. Gypsum mortar was used for later repair in the 18th century. The results show much stronger damage due to earthquakes than previously thought.

Radiocarbon (14C) dating was performed on samples from the prehistoric settlement at Makriyalos, northern Greece, a “flat extended” (rather than tell) site. Two separate occupation phases, Makriyalos I and II, were clearly distinguished on different sides of a low hill and belonged to the Late Neolithic I and II periods, respectively. Individual phases related to the use of circuit ditches and borrow pits were also recognized and dated. Phase modeling was applied in order to establish the sequence and duration of use of different features. The earliest activity seems to be around 5450 BC, among the earliest dates in northern Greece for the beginning of the LN and perhaps reflecting some earlier activity. The transition from LNI to LNII occurred at around 4950 BC without discontinuity earlier than other sites in Macedonia but perhaps same time as Thessaly. Intermediate ditch cutting phases occurred at 5300 and 5050 BC. A cemetery in the area of the settlement, initially thought to relate to the LNII phase of the settlement, was shown to date in the EBA period (beginning of 3rd millennium BC).

Marine reservoir age is an important component for correction in radiocarbon (14C) dating of marine and coastal samples. 14C concentration in pre-bomb marine samples of known age are used to derive marine reservoir age of a region. Annually banded coral from Landfall island in the northern Andaman has been analyzed for its 14C concentration during the pre-bomb period 1948–1951. 14C age and reservoir effect (∆R) are reported for these pre-bomb coral samples from the northern Andaman region. The mean 14C age of 331 ± 61 yr BP was obtained for the period 1948–1951 with an average reservoir age correction of –138 ± 61 yr. This reservoir age correction is lowest reported from the northern Indian Ocean. ∆R value of the northern Andaman and the Bay of Bengal appears lower than that of southern Andaman. The ∆R values obtained using mollusk shells and coral from the Andaman region shows large variability. The lower reservoir age correction for the Landfall Island situated in the northern part of the Andaman archipelago, could result due to freshwater flux and reduced upwelling in the region.

The Rio Grande Cone is a major fanlike depositional feature in the continental slope of the Pelotas Basin, Southern Brazil. Two representative sediment cores collected in the Cone area were retrieved using a piston core device. In this work, the organic matter (OM) in the sediments was characterized for a continental vs. marine origin using chemical proxies to help constrain the origin of gas in hydrates. The main contribution of OM was from marine organic carbon based on the stable carbon isotope (δ13C-org) and total organic carbon/total nitrogen ratio (TOC:TN) analyses. In addition, the 14C data showed important information about the origin of the OM and we suggest some factors that could modify the original organic matter and therefore mask the “real” 14C ages: (1) biological activity that could modify the carbon isotopic composition of bulk terrestrial organic matter values, (2) the existence of younger sediments from mass wasting deposits unconformably overlying older sediments, and (3) the deep-sediment-sourced methane contribution due to the input of “old” (>50 ka) organic compounds from migrating fluids.

Annually resolved tree-ring samples of the time period 1625–1510 BCE were analyzed from the German oak tree-ring chronology. Blocks of the same tree rings were previously used to generate IntCal calibration data. The new dataset shows an offset to the calibration data IntCal13 of 24 years and resembles annual data for the same time period derived from tree-ring records in other growth locations. A subset of samples of the period 1625–1585 BCE was additionally measured in three other laboratories (ETH, AAR, AA) for quality control.

There are few papers that focus on optically stimulated luminescence (OSL) dating of earthen mortars. These mortars are abundant in historical buildings in northwestern Spain. The Basílica da AscensiónyForno da Santa building is an unfinished church built on a previous structure that was transformed into a crypt (Allariz, Ourense, NW Spain). Previous archaeological studies established a sequence of phases of construction, the first dating back to the Iron Age, with significant changes occurring in the Early and Late Medieval ages. The only datable material in the crypt is earthen mortar. Thus, eight mortar samples (seven joint mortars and one wall infill) were taken, seven of them dated by OSL. The dose rate was assessed, and the expected equivalent doses estimated based on the established archaeological age. Several grain sizes (from fine to coarse) were used in small multigrain aliquots to assess the equivalent doses and ages. No evidence of partial bleaching was observed in most samples and grain sizes. The resulting ages are younger than expected for most samples. This is explained by the fact that joints were repaired with new mortar from the 16th century onwards.

At archaeological sites located on islands or near the coast, the potential exists for lipid extracts of potsherds to contain fatty acids (FA) from both aquatic and terrestrial organisms, meaning that consideration must be given to marine reservoir effects (MRE) in radiocarbon (14C) analyses. Here we studied the site of Bornais (Outer Hebrides, UK) where a local MRE, ΔR of –65 ± 45 yr was determined through the paired 14C determinations of terrestrial and marine faunal bones. Lipid analysis of 49 potsherds, revealed aquatic biomarkers in 45% of the vessels, and δ13C values of C16:0 and C18:0 FAs revealed ruminant and marine product mixing for 71% of the vessels. Compound-specific 14C analysis (CSRA) of FAs yielded intermediate 14C ages between those of terrestrial and marine bones from the same contexts, confirming an MRE existed. A database containing δ13C values for FAs from reference terrestrial and marine organisms provided endmembers for calculating the percentage marine-derived C (%marine) in FAs. We show that lipid 14C dates can be corrected using determined %marine and ΔR values, such that pottery vessels from coastal locations can be 14C dated by CSRA of FAs.

Dating lime mortar shows great potential for establishing the chronology of a construction. The basic premise of mortar dating by optically stimulated luminescence (OSL) is that quartz in the sand used for making mortar has been optically zeroed during the preparation process (optical bleaching). The moment to be dated is the last exposure of sand grains to light, before being embedded within the masonry and hidden from light. However, the main problem is the frequent partial and heterogeneous bleaching of grains, and this led us to use the single grain technique (SG-OSL) systematically. Some theoretical and experimental aspects of a new statistical treatment (the EED model, as exponential exposure distribution) are detailed and discussed. Our experience shows that SG-OSL dating of mortars is successful in a majority of situations. In a minority of cases (around 15%) difficulties originate when there is inappropriate OSL behavior of grains, and thus OSL dating is not possible. In the other cases, good agreement was obtained between OSL ages and the reference ones for a series of samples from a variety of ages and situations, even in the case of poorly bleached material. Anyway, the present situation of OSL dating methodology justifies the systematic use of SG-OSL in the dating of masonry today.

Eighteen new high-precision radiocarbon (14C) dates obtained for dendrochronologically dated wood from Bodegraven, the Netherlands are reported. They are relevant for establishing the revised calibration curve around the time of the Bronze Age Santorini eruption. Most of our new data overlap within one sigma with IntCal13, but a few data points are slightly increased in 14C age compared to IntCal13.